Since there really is no such thing as PERFECT …
Let me suggest that you should practice until you feel totally comfortable.
That SHOULD mean practice a lot.
Only YOU know how much practice that is.
Think how many times someone who loved you "suggested" you say "THANK YOU." when you got something - when you were a child.
I see mothers doing that for their children - A LOT.
And still we know some adults who don't say, "Thank you." when they get something.
Or, "You're welcome." when they are thanked.
They didn't practice enough.
And it shows.
It is bad manners.
Practice until what you are expected to say feels like it is so much a part of your DNA that you don't have to think about it for a nanosecond.
Repetition - repetition - repetition …
Today's One Point Wiki Wiki eXpression is "Get a word in edgewise."
It means to manage to say something during a conversation - the other person won't let you talk.
(I used to work with a person who liked to talk and hated to listen. They wouldn't let me get a word in edgewise. Meeting them every day for a week was not very pleasant.)